An agricultural windrower is a large machine used to harvest a variety of crops from a field. The windrower includes a traction unit and a cutting platform mounted to the front of the traction unit. During a harvesting operation, the cutting platform cuts ripened crop from the field. The crop is transported to the rear of the cutting platform and forming shields form a windrow of the crop between the tires of the vehicle for natural dry down of the crop (or, alternatively, windrows formed at the ends of the cutting platform). A subsequent field operation picks up the windrows for further processing, such as separating and cleaning in the case of grain crops, or baling or chopping in the case of hay.
Self-propelled windrowers typically include a pair of drive wheels and one or more caster wheels which are carried by a machine frame and free to rotate about a generally vertical axis 360°. Windrowers are typically driven through a dual-path hydrostatic system. Speed changes are made by adjusting the speed of both drive (front) wheels simultaneously. Direction changes are made by adjusting the relative speed of the drive wheels. The castered rear wheels allow the machine to pivot during direction changes. A caster wheel assembly typically includes a shaft defining an axis of rotation, a fork rigidly attached to the bottom end of the shaft, and a caster wheel coupled with the distal ends of the fork.
Steering characteristics are dependent on such things as steering linkages, hydrostatic pump reaction time, the machine's turning inertia, and caster turn resistance. There is a tendency for a steering input to have a slow reaction (under steer) at initiation, then a tendency to keep turning (over steer) when the input is stopped or reversed. Because of this, control of the machine can be difficult, particularly at higher transport speeds. Windrowers typically have a maximum speed in transport in the 15 miles per hour (mph) range. Transport speeds up to 25 mph would be an advantage in the market. This requires better machine controllability at higher speeds without sacrificing agility (spin steer) at lower speeds.
At least one third party competitor advertises a windrower with a transport speed of 23 mph. This is achieved by reversing the operator's station and operating the machine in the reverse direction for transport.
A secondary problem with current windrower drives is transport of the windrower with the platform removed. Reaction delay can be particularly pronounced if the machine is operated without the platform due to the added weight on the casters and the resulting increase in turn resistance.
It may also be desirable to dismount a platform and transport it by towing it behind the traction unit. This is difficult with current windrower configurations because the rear of the windrower, which is controlled by the drive (front) wheels, must swing in reaction to steering inputs and, conversely, inputs from the towed platform must be resisted by the drive wheels.
The assignee of the present invention currently instructs operators to not transport a windrower traction unit with the platform dismounted. Wider platforms designed to be removed easily from the traction unit increase the importance of transport without a platform.
It is known to transport a windrower without the platform by providing a portable weight to carry in place of the platform during transport. This balances the traction unit and allows “slow speed transport” with the platform in tow. Disadvantages to this approach include the logistics of having the weight with the traction unit when needed, the inconvenience of attaching and removing the weight, and the added cost of the option.
What is needed in the art is a windrower which allows a cutting platform to be easily and effectively towed (or pushed) in transport.